Question: ${9 \div 0.4 = {?}}$
Answer: $ {9 \div 0.4 = 9 \div \dfrac{4}{10}} $ $ {\phantom{9 \div 0.4} = 9 \div \dfrac{2}{5}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {9 \div \dfrac{2}{5} = 9 \times \dfrac{5}{2}} $ $ {\phantom{9 \div \dfrac{2}{5}} = \dfrac{9 \times 5}{2}} $ $ {\phantom{9 \div \dfrac{2}{5}} = \dfrac{45}{2}} $ $ {\phantom{9 \div \dfrac{2}{5}} = 22.5} $